US9949677B2 - Implantable oximetric measurement apparatus and method of use - Google Patents

Abstract

Embodiments provide an apparatus, system, kit and method for in vivo measurement of blood oxygen saturation (BAS). One embodiment provides an implantable apparatus for measuring BAS comprising a housing, emitter, detector, processor and power source. The housing is configured to be injected through a tissue penetrating device into a target tissue site (TS). The emitter is configured to emit light into the TS to measure BAS, the emitted light having at least one wavelength (LOW) whose absorbance is related to a BAS. The detector is configured to receive light reflected from the TS, detect light at the LOW and generate a detector output signal (DOS) responsive to an intensity of the detected light. The processor is operably coupled to the detector and emitter to send signals to the emitter to emit light and receive the DOS and includes logic for calculating a BAS and generate a signal encoding the BAS.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority U.S. Provisional Patent Application No. 61/627,999 filed Oct. 21, 2011; entitled, Implantable Oximetric Measurement Apparatus and Method of Use, which is fully incorporated by reference for all purposes.

FIELD OF THE INVENTION

Embodiments described herein relate to an apparatus, system and method for performing in vivo measurements in the body of a living animal. More specifically, embodiments described herein relate to an apparatus, system and method for performing in vivo oximetry measurements in the body of a human patient.

BACKGROUND

Blood oxygen saturation, herein oxygen saturation is a measurement corresponding to the degree to which the hemoglobin molecule is saturated with oxygen. Oxygen saturation provides a wealth of information about a patient's health including particular conditions. It can, for example, provide information on a person's pulmonary function, cardiovascular function, circulation and hematologic state. The current standard method for measurement of oxygen saturation is a technique known as oximetry. Oximetry is based on the principle that the color of blood is related to the oxygen saturation level (SaO₂) in the blood. Oximetric devices use a light source and light dectector. Light from the light source (known as afferent light) is emitted into the patient's blood directly via a catheter or indirectly via a transcutaneous probe placed on the skin. Typically, the light source emits at least two separate wavelengths of light with each wavelength having different absorption curves such that the ratio of the two absorptions is unique for the range of oxygen saturations from 0% through 100% saturation. The detector detects light that is transmitted through the patient's blood known as efferent light. As is explained in more detail below, the nature of the efferent light depends on the blood oxygen saturation sated of the patient's blood. The efferent light can be collected directly from a catheter positioned in the patient's vasculature or indirectly via a transcutaneous probe. Information from the detector can then be sent to a processor which includes software for analyzing the afferent and efferent light in order to determine the level of oxygen contained in the patient's blood. More specifically, the software contains routines for analyzing the ratio of absorbances of the two emitted wavelengths and then determining blood oxygen saturation based on that ratio.

Current oximetry devices include probes that are placed on the skin or catheters that are placed in an artery such as the pulmonary artery. However both of the devices are unable to provide an indication of what the localized oxygen saturation is at a tissue site beneath the skin (other than the finger tip). Rather, they only provide an indication of what the systemic blood oxygen saturation is. Localized blood oxygen saturation for tissue sites beneath the skin can be used to diagnose a number of conditions including any number of conditions causing localized ischemia such as deep vein thrombosis, peripheral vascular occlusion, edema and cancer. What is needed is a device and method for measuring blood oxygen saturation at a localized level at a selected tissue site to facilitate diagnose of these and other diseases and conditions.

Also, current oximetric devices cannot be left in place for any extended period of time due to the requirement of having an in dwelling catheter or having a finger probe attached to the oximeter. What is also needed is an oximetric measurement device which can be left within the patient for an extended period without requiring the patient to be bedridden or otherwise tethered to an instrument.

BRIEF DESCRIPTION OF THE INVENTION

Embodiments of the invention provide an apparatus, system and method for the in vivo measurement of blood oxygen saturation. Various embodiments provide an apparatus, system, and method for measurement of localized blood oxygen saturation, using an implantable device. Many embodiments provide an apparatus for measurement of localized blood oxygen saturation which can be placed beneath the skin surface at a selected target tissue site using a syringe or other tissue penetrating device such as a trocar. In use such embodiments allow for the localized detection of underperfused and/or hypoxic tissue. Such embodiments are particularly useful for the detection of various diseases and conditions such as cancer, peripheral arterial stenosis, peripheral neuropathy, diabetes and other condition

One embodiment provides an apparatus for measurement of blood oxygen saturation in a patient comprising a housing having a wall and an interior volume and an optical emitter, optical detector, controller and power source, one or more of which are positioned on or within the housing. The housing can have one or more of a size, shape and column strength to be injected through a hollow tissue penetrating device (e.g., a syringe, trocar, catheter or like device) into a target tissue site beneath the skin of the patient such as an intramuscular site by the application of a force to the housing, for example by the plunger of a syringe. At least a portion of the housing wall comprises an optically transparent material such as glass or a transparent polymer to allow light to pass in and out of the housing. The emitter is arranged and configured to emit light through the transparent portion of the housing wall and into the tissue site to measure a blood oxygen saturation within the tissue site. The light emitted from the emitter has at least one wavelength whose absorbance is related to a level of blood oxygen saturation and a second wavelength whose absorbance is substantially unaffected by the oxygenated state of blood. The emitted light will typically include a first and a second wavelength with the first wavelength in the range of about 600 to 750 nm and the second wavelength in the range of about 850 to 1000 nm. In specific embodiments, the first wavelength is about 660 nm and the second wavelength is in the range of about 900 to 950 nm. Additional numbers and ranges of wavelengths are also contemplated.

The optical detector is positioned and arranged to receive light reflected from the tissue site and detect at least the first and second wavelengths and generate a detector output signal responsive to an intensity of the detected light. The controller is positioned within the housing and is operably coupled to the detector and emitter to send signals to the emitter to emit light and receive the detector output signal. The controller can include logic for calculating a blood oxygen saturation level using the detector output signal and generating a signal encoding the blood oxygen saturation level. In particular embodiments, the controller can correspond to a microprocessor with the logic corresponding to software modules operable on the microprocessor. The power source is positioned within the housing for powering at least one of the controller, the emitter or the detector. Typically, the power source is directly coupled to at least the controller but may be coupled to other components as well including for example a recharging device such as an energy harvesting mechanism. In many embodiments, the power source comprises a miniature lithium battery known in the art such as a lithium ion battery.

In various embodiments of the invention, the apparatus may include a magnetic hook which may comprise a magnet or a non-magnetic ferrous structure positioned on or within the housing to allow the apparatus to be removed from the tissue site or otherwise manipulated beneath the skin to facilitate removal using a removal tool containing a magnet or magnetized portion. The force of magnetic attraction between the hook and the removal tool magnetic portion being sufficient to pull the apparatus from the tissue site to the skin surface (i.e., beneath the skin surface) so that the apparatus can be easily removed with a very shallow incision in the skin. The removal tool may comprise a magnet itself or a finger grippable shaft attached to the magnet, allowing a physician to have finer control over the second magnet. In a particular embodiment, the magnet on the removal tool may comprise an adjustable electromagnet allowing the physician to adjust the amount of magnetic force used to remove the apparatus. In a related embodiment, the magnetic hook may comprise a ferrous-based suture or wire, herein, “a pull wire”, attached to the exterior surface of the housing which allows the physician to first pull the wire or suture to the skin surface using the removal tool and then pull the apparatus out to the tissue using the pull wire. In some embodiments, the pull wire can include a loop on its non-attached end to facilitate grasping of the wire once it is brought near the skin surface. The benefits of using the pull wire include one or more of the following: i) less magnetic force is required to remove the pull wire then that required to remove the whole housing allowing use of a less powerful second magnet; and ii) the physician can more easily and controllably remove the entire apparatus using the pull wire then removal by magnetic attraction alone which should reduce both tissue trauma and pain. In some embodiments, a combination of an internal magnetic hook and an external ferrous-based pull wire can be used to further facilitate atraumatic removal of the apparatus. Removal of the apparatus can also be facilitated by fabricating portions of the housing from radio-opaque, echogenic or other materials visible under a selected medical imaging modality and/or attaching to the housing one or more medical imaging markers such as radio-opaque and/or echogenic markers.

In various embodiments of the invention, all or a portion of the apparatus housing can be fabricated from shape memory materials such as nickel titanium alloys allowing the apparatus to be placed at the selected tissue sit; with the apparatus having a first size and shape and then upon exposure to body temperature within the tissue site, the apparatus expands to a second size and shape. In particular embodiments, the housing can be configured expand so as to anchor the housing at the tissue site. For example, in one or more embodiments, the housing can be fabricated from shape memory materials configured to expand to an hour glass or other like shape with the ends of the housing flaring out to hold the apparatus in place at the tissue site. In use, such embodiments allow the housing to have a smaller size to facilitate placement at the selected tissue site and then to expand to the larger size and/or shape to anchor the apparatus at the tissue site so as minimize movement of the apparatus once placed at the site. In related embodiments, all or a portion of the housing can be fabricated from shape memory materials having pseudo-elastic properties such as nickel titanium alloys (an example including NITINOL) configured to undergo a change in stiffness upon exposure to body temperature. Typically, this change will entail going from a more rigid state to a more flexible state (though the reverse is also contemplated). Such embodiments allow the apparatus to have a more rigid quality to facilitate insertion at the tissue site and then once placed, become more flexible to allow the housing to bend and flex with movement of the body including movement of tissue at the tissue site. In one embodiment, the center portion of the housing can be configured from a shape memory material which becomes elastic at body temperature allowing the center portion of the housing to bend and flex with movement of body tissue. Such embodiments of the housing having pseudo elastic properties also facilitate removal of the apparatus from the patient's body and reduce trauma since the housing can bend when grasp by a forceps or attracted by a magnetic removal tool allowing the housing to be bent up toward the skin surface or otherwise manipulated while imparting less force to surrounding tissue.

In other aspects of the invention, embodiments of the measurement apparatus can be adapted for numerous applications in the medical field including diagnostic and prognostic applications. Such applications can include, for example, tumor monitoring including monitoring a tumor for the efficacy of chemotherapy by using the oxygenated state of tissue in and around the tumor as an indication of the size and viability of the tumor. In use, such tumor monitoring applications allow a course of chemotherapy to be titrated responsive to the effects on the tumor of the chemotherapy. This improves both treatment efficacy and long term patient tolerance. For example, the dose of a particular chemotherapeutic compound with side effects such as nausea could be reduced upon determination that the tumor is shrinking, improving patient tolerance.

In another application, an embodiment of the oxygen saturation measurement apparatus can be adapted for monitoring the health and/or viability of an organ transplant by measuring the oxygenated state of tissue in and around the organ. Change such as decreases in oxygen saturation including rapid decreases being indicative of tissue rejection or the onset of tissue rejection. This in turn, allows time for rapid medical intervention to save the transplanted organ. In another application, embodiments of the apparatus can be used to monitor for oxygen saturation in the extremities of diabetic patients (who are prone to develop neuropathy in their extremities) allowing for medical intervention before the development of neuropathy. In still other applications, embodiments of the invention can be used for monitoring patients who have chronic obstructive pulmonary disease (COPD) or other respiratory disorders allowing for early diagnosis and treatment of an adverse respiratory state in such patients. Related embodiments can be use to monitor oxygen saturation levels of patients having congestive heart failure (CHF) again allowing for early diagnosis and treatment of various related conditions, e.g., pulmonary edema, before they become life threatening. In still other applications, embodiments of the invention can be used to monitor the progress of wound healing at a selected tissue site allowing for the early detection and treatment of acute conditions such as infection as well as monitoring the longer term progress of the wound healing process. Infection may be characterized by either a rise or fall in tissue oxygen saturation at the site depending upon the type of bacteria. For example, changes (e.g., lower) in the levels of oxygenation may be utilized as biomarkers/predictors of slower or other atypical healing requiring medical intervention (e.g., through the administration of one or more drugs, such as growth hormone, erythropoietin or other like compounds). Such predictions can be achieved by developing correlations between the time course of the healing process and levels of tissue oxygen saturation at site including rates of change of oxygen saturation. Still other related applications are also contemplated by various embodiments of the invention as will be known to those skilled in the medical diagnostic and other related arts. The features and attributes of the oxygen saturation measurement apparatus can be customized for each application, with such features including one or more of the size, shape, surface coatings, emitted and detector configuration and the wavelength, intensity and duty cycle of the emitted wavelength and other like factors. For example, the wavelength, intensity and duty cycle of the emitted light may be fine tuned for increased sensitivity to detect lower levels of blood oxygen saturation found in one or more of deep vein thrombosis, infected or tumerous tissue.

In yet another aspect of the invention, embodiments of the invention provide a kit for measuring blood oxygen saturation comprising embodiments of the oxygen saturation measurement apparatus described herein and instructions for using the apparatus alone and/or in conjunction with a monitoring device including a portable monitoring device which allows for the monitoring of signals transmitted from the apparatus. Such signals can include information on measured oxygen saturation. The instructions may either be in printed form or in electronic media such as a ROM or other memory resources integral to the monitoring device or a CDROM. The instructions may include specific instruction for establishing a communications link between the apparatus and the portable monitoring device which can be a custom device or an off the shelf cell phone or PDA like device. Further, specific embodiments of the instructions can describe how to couple and use the apparatus with one or more of an APPLE IPHONE, IPAD, IPOD or like portable device running one or more software applications for deep vein thrombosis detection.

Embodiments of the instructions can also include specific instructions for doing one or more of the following: calibrating the apparatus, taking baseline measurements, instructions for how to use the apparatus to detect various conditions such as deep vein thrombosis; and instructions for reading and/or interpreting a display of the portable monitoring device to determine the presence of a deep vein thrombosis. These and other features and embodiments of the invention are described in detail in the body of specification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating an embodiment of an implantable oxymetric measurement apparatus positioned at target tissue site within a patient.

FIG. 2 is a top view illustrating an embodiment of an implantable oxymetric measurement apparatus.

FIGS. 3a-3dare cross sectional orthogonal views of the embodiment ofFIG. 2, illustrating the arrangement and positioning of components of the implantable oxymetric measurement apparatus at various locations over the length of the apparatus.

FIGS. 4a-4cillustrate placement of an embodiment of an oxymetric measurement apparatus at a target tissue site within a patient using a tissue penetrating device such as a syringe.

FIGS. 4d-4fillustrate an embodiment of an oxymetric measurement apparatus having a biodegradable tissue penetrating attachment.FIGS. 4dand 4eillustrate insertion of the apparatus into tissue andFIG. 4fillustrates the shape of the apparatus after the attachment has degraded to yield an atraumatic shape for the attachment housing.

FIG. 5 is a lateral view illustrating the position and operation of an embodiment of an emitter and detector used in one or more embodiments of the invention.

FIG. 6 is a block diagram illustrating an embodiment of a controller having one or more software modules for control of one or more operations of embodiments of the oximetric measurement apparatus.

FIG. 7 illustrates use of a monitoring device and one or more oximetric measurement apparati to monitor the oxygen saturation of a patient.

FIGS. 8a-8cillustrates embodiments of an oximetric measurement apparatus having a magnetic hook and use of a magnetic removal tool to remove the measurement apparatus by the magnetic hook.

FIG. 9 is a perspective view illustrating an embodiment of an oximetric measurement kit including an oximetric measurement apparatus and instructions for using the oximetric measurement apparatus.

DETAILED DESCRIPTION OF THE INVENTION

Referring now toFIGS. 1-9, an embodiment of anapparatus10, for measurement of blood oxygen saturation in a patient P comprises ahousing20 having a wall25 (having an exterior andinterior surface21 and22)interior volume26; and anoptical emitter30,optical detector40, controller50, electronic devices60 and power source70 (also referred to herein as power supply70). One or more of these components may be positioned within or on thehousing20. Additionally, one or more of these or other electrical components ofapparatus10 may be positioned on or otherwise electrically coupled to a printed circuit board15 (or like component) to facilitate ease of manufacturing and/or achieve a selected form factor for insertion and fit within theinterior volume26 ofhousing20. In particular embodiments, printedcircuit board15 can be configured to allow for connection of electrical components ofapparatus10 on bothsides16 and17 of the board to allow for space savings withinhousing20. For example in one embodiment, anintegrated circuit53 corresponding to controller50 or an ASIC55 may be placed on abottom side17 ofboard15 while other components such asemitter30,detector40 and devices60 are placed on thetop side16. Devices60 may include for example, resistors capacitors, inductors and may be arranged to form one or more circuits61, for example an LC circuit, or RC circuit61.

Housing20 has a size, shape and column strength to be injected or otherwise advanced through a hollowtissue penetrating device200 such as a syringe201 into a target tissue site TS beneath the skin S of the patient P, (for example, an intra-muscular site within muscle M) by the application of force to the housing as is shown in the embodiments ofFIGS. 1 and 4a-4c. Typically, the force will be applied to aproximal portion23p(the end which enters tissue last) ofhousing20, for example by theplunger202 of syringe201. In various embodiments, use of othertissue penetrating devices200 is also contemplated for advancement ofapparatus10 into tissue including one or more of a trocar, catheter or endoscope. In particular embodiments,housing10 can be configured to be inserted directly into tissue without use of atissue penetration device200 by the application of force onto a proximal23por other portion ofhousing20.

In particular embodiments,housing20 can have a cylindrical like shape with its distal end23 (the end which enters tissue first) having a tapered shape or other tissue penetrating shape to facilitate tissue penetration. In these and related embodiments,housing20 can comprise abody27 and acap28 which is hermetically sealed tobody27 using an adhesive or other sealing method known in the art (e.g., ultrasound welding, etc.).

In particular embodiments shown inFIGS. 4d-4f, atissue penetrating attachment20tpacan be attached to thedistal end23 ofhousing20.Tissue penetrating attachment20tpacan have a pointed or other tissue penetrating shape and is desirably fabricated from a biodegradable material such as maltose, sucrose, PGLA (Poly Lactic-co-Glycolic Acid), or other like material which degrades soon (e.g., 1 to 2 minutes to an hour) afterapparatus10 is positioned at tissue site TS. Use of the biodegradable material for thetissue penetrating attachment20tpaallowsapparatus10 to be readily inserted into tissue (alone or with use of a syringe) and then after insertion, have thetissue penetrating attachment20tpadegrade to yield a smoothatraumatic shape23 as for the distal end of23 ofhousing20 so as to provide for the long term biocompatibility ofapparatus10 at a tissue site TS. In use, this allows forapparatus10 to be readily tissue insertable on the one hand and on the other, provide for the long term measurement of blood oxygen saturation levels.

The length201 ofhousing20 can be in the range of about 4 to 10 cms, with specific embodiments of 5, 6, 7, 8 and 9 cms, while the width20wcan be in the range of about 0.5 to 2 mm, with specific embodiments of 1, 1.25 and 1.5 mms. Length201 and width20ware desirably selected to allow sufficient interior volume for placement ofemitter30,detector40 controller50, devices60 and power source70 withinhousing20. In particular embodiments, length201 and width20wcan be selected to allow for a linear arrangement ofemitter30,detector40, controller50, devices60 and power source70.

In various embodiments, the column strength ofhousing20 can range from about 0.1 lbs (force) to 5 lbs, with specific embodiments of 0.2, 0.25, 0.3, 0.5, 0.75, 0.8, 1.0, 2.0, 2.5, 3 and 4 lbs force. The column strength ofhousing20 can be achieved through one more of the selection of materials for the housing as well as the thickness ofwall25. Suitable materials forhousing20 in this regard include various biocompatible polymers known in the art including various rigid biocompatible polymers such as PET, HDPE, polymethylmethacrylate (PMMA) and like materials. The column strength of one or more of these materials, such as HDPE may be increased by exposure to electron beam to radiation to achieve cross linking of polymer chains as is known in the catheter arts. Also in various embodiments, all or portions of the housing can be fabricated from radio-opaque and/or echogenic materials to achieve visualization of the housing under fluoroscopy, ultrasound or other medical imaging modality. In related embodiments,housing20 can include one or moremedical imaging markers24 such as radio-opaque, echogenic, or other marker fabricated from a material visible under a selected medical imaging modality.

In various embodiments, all or a portion of thehousing20 can include a coating21csuch as silicone, PTFE or polyurethane to achieve one or more of the following: i) impart a greater degree of biocompatibility tohousing20; ii) reduce the amount of cellular and other bio-adhesion toexterior surface21; and iii) provide a lubricous surface facilitating placement of the housing a selected tissue site. In an alternative or additional embodiment, coating21ccan also include a drug eluting coating such as paclitaxel or various steroids for reducing cellular adhesion toexterior surface21.

At least a portion of thehousing wall25 comprises an optically transparent material such as glass or an optically transparent polymer to allow light to pass in and out of the housing. Suitable optically transparent materials include glass, PMMA, polydimethylsiloxane and hydrogels including high stiffness hydrogels. In some embodiments, theentire housing20 is fabricated from an optically transparent material. In others, the housing includes an optical window29 (fabricated from optically transparent material) under which, theemitter30 anddetector40 are positioned.Emitter30 is arranged and configured to emit light throughoptical window29 and into tissue site to measure a blood oxygen saturation within the tissue site. One or both of theemitter30 anddetector40 can be positioned flush against theinside surface22 ofwall25 or may be recessed a selected amount and may be positioned at a selectable angle with respect to the plane ofwall25 so as to achieve a desired angle of incidence and reflectance.

According to one or more embodiments,emitter30 can comprise a single or multiple LEDS. It may also include various single or multi-wavelength LEDS known in the art. The light emitted31 fromemitter30 has at least one wavelength32 whose absorbance is related to a level of blood oxygen saturation and a second wavelength33 whose absorbance is substantially unaffected by the oxygenated state of blood. First wavelength32 can be in the range of about 600 to 750 nm and the second wavelength33 in the range of about 850 to 1000 nm. In specific embodiments, the first wavelength is about 660 nm and the second wavelength is in the range of about 900 to 950 nm. Additional values and ranges of wavelengths are also contemplated. Both first and second wavelengths32 and33, as well their intensity, can be adjusted depending upon the selected tissue site TS, for example, organ O versus muscle M, with adjustments made for the optical properties of a specific tissue site (e.g., absorbance of specific wavelengths). In particular embodiments, the intensity of one or both of wavelengths32 and33 can be adjusted to penetrate a selecteddistance35 into the tissue at the target tissue site, for example penetrating up to about 0.5 cm, 1 cm, up to about 2 cm and up to about 3 cms, with larger and smaller depths contemplated. Thepenetration depth35 and corresponding intensity can be adjusted depending upon the application, for example, tumor monitoring, wound healing monitoring, CHF monitoring or COPD monitoring. Additionally, the intensity of wavelengths32 and33 can be adjusted over time can be adjusted (typically increased) to compensate for the buildup of adhered protein, cells and other tissue onhousing exterior surface21 which may reduce the transmission of light throughoptical window29 and/orwall25.

Theoptical detector40 is positioned and arranged to receive light reflected from the tissue site TS and detect at least one wavelength and generate a detector output signal responsive to an intensity of the detected light. In various embodiments,detector40 can comprise one or more of a photodiode, photo transistor, photomultiplier, CCD or other like device. Also,desirably detector40 is configured to detect light at multiple wavelengths (e.g., two, three, four, etc).Detector40 can be positioned in theinterior surface22 ofhousing wall25 or it may be recessed.

Controller50 is operably coupled to one or more components ofapparatus10 so as to control various components and/or operations of the apparatus. This may be accomplished by coupling the controller to printedcircuit board15 on which one or more other electric components are coupled. In various embodiments, controller50 may correspond to one or more of analog control circuitry, a state device, a microprocessor or software operable on a microprocessor or other like device. In particular embodiments, controller50 is coupled toemitter30 anddetector40 to sendsignals38 to theemitter30 to emit light and receivesignals41 from thedetector40 corresponding to intensity of detected light. Controller50 may include logic such as software, firmware, hardware or combinations thereof for controlling one or more operations ofapparatus10, such as emission of light byemitter30, power management, power coupling, calculation of blood oxygen levels and signaling information on such levels to an external device. Controller50 may also be incorporated into an application specific integrated circuit or ASIC55 which may also include other components ofapparatus10 such asdetector30,emitter40, devices60, power source70,memory device80 and an RF orother communication device90. As described above controller50 may be coupled to acircuit board15 to allow coupling of controller50 to these and other components.

Controller50 may also be coupled to amemory device80, which may correspond to ROM, RAM, DRAM or other memory device known in the art.Memory device80 may include one or more software modules51 for controlling one or more operations of controller50 andapparatus10. Modules51 can be configured to be uploaded to controller50 for example by programming resident within controller50.Memory device80 may also be configured to be reprogrammed, for example by means ofcommunication device90 to allow for downloading of different programs for control and operation ofapparatus10.

In particular embodiments, controller50 corresponds to a microprocessor and includes one or more software modules51 for calculating blood oxygen saturation or a related parameter using thedetector output signal41 and generating anoutput signal52 corresponding to that saturation level. Modules51 may also be configured to perform one or more of the following operations: i)store output signal52 as a storedvalue53 inmemory50mof controller50 or aseparate memory device80; ii) sendoutput signal52 to anRF communication device90 for sending an RF signal91 (corresponding to signal52) to an external device100; iii)direct memory device80 to send a plurality of signals52 (corresponding to a plurality of stored values53) tocommunication device90 for wireless communication with an external device100 (e.g., either in continuous or a burst mode, either of which can be in response to asignal92 from device100 or a condition module51 such as an oxygen saturation being below a threshold); and iv) initiate one or more oxygen saturation measurements by sending ofsignals38 toemitter30 either at selected time intervals or in response to an input such as asignal92 from external device100. For embodiments ofapparatus10 including acommunication device90, module51 can be programmed to transmitsignals52,91 continuously, at set time intervals or in response to one or more conditions being met such as oxygen saturation falling below a set threshold (e.g., 95, 90% etc.). The later case can be tailored for monitoring bedridden patients including critical care patients with the specific oxygen threshold dictated by the particular patient and their condition (e.g., peripheral claudication). In use, these and related embodiments eliminate the need to have critical care and other bedridden patients tethered to an oximeter (either via transcutaneous probe or a pulmonary arterial catheter). Also,multiple apparati10 can be placed at a number of locations in the patient's body such as in one or more of their extremities in order to get a broader picture of perfusion and tissue oxygenation throughout the patient's body. In particular embodiments,apparatus10 can be placed in each extremity (e.g. arms and legs) so that the medical care giver can ascertain if uniform perfusion is occurring in these locations, and if not, be able to compare perfusion/oxygenation in one limb with another, for example leg vs. arm or arm vs. arm. In a related or alternative embodiment at least a first andsecond apparatus10 can be placed at two target tissue sites TS with blood oxygen measurement at the first site being compared to the second site. This can allow for determining if one site is hypoxic/underperfused compared to the second site as well as if both sites are hypoxic/underperfused to allow for a more comprehensive determination of one or more of deep vein thrombosis, transplant tissue viability/health, or tumor location or state. In another related embodiment,multiple apparati10 can be placed at the same or different tissue sites in order to develop a map of blood oxygen saturation for a given tissue site TS or multiple tissue sites.

Power source70 is configured to power one or more components ofapparatus10. In many embodiments, power source70 is configured to power at least one ofemitter30,detector40, controller50, electronic devices60 andcommunication device90. Typically, the power source is directly coupled to at least the controller50 but may be coupled to other components as well including for example, a recharging device such as an energy harvesting mechanism. Typically, power source70 is positioned withinhousing20 but also may be disposed on the housing exterior. In many embodiments, the power source70 comprises a miniature battery71 such as a lithium or lithium ion battery which can include rechargeable batteries. Desirably, the battery71 has a form factor such as a cylindrical form factor which corresponds to the shape of housinginterior volume26. In one alternative embodiment, power source70 may also correspond to a super capacitor.

In various embodiments power source70 may also include a conductive coil72 arranged and configured for recharging various embodiments of a rechargeable power source70 (e.g., a rechargeable battery, super capacitor, etc.) source via conductive coupling methods known in the art. In particular embodiments, coil72 can be wrapped around a battery71 in order to conserve space insidehousing20. Coil72 may also be configured as anantenna96 forcommunication device90. In related embodiments, coil72 can also be configured as amagnetic hook75 for removingapparatus10 from tissue site TS using amagnetic removal tool210 as is described below. In such embodiments, coil72 is fabricated from ferrous material and may be magnetized or configured as an electro-magnet powered by a battery power source70.

Communication device90 can comprise one or more of a radio frequency (RF), optical or acoustical based communication device. In preferred embodiments,communication device90 can comprise an RF chip configured to send and receive signals at one or more frequencies or ranges of frequencies. In various embodiments, the range of frequencies can be in a range of about 400 MHz to 6 GHz with a specific embodiment of about 402 to 405 MHz so as to correspond to the Medical Implant Communications Services (MICS) standard established by the Federal Communications Commission (FCC).Communication device90 can be configured to wirelessly communicate with an external device100 (e.g. a portable communication device101 such as a cell phone) described below so as to sendsignals91 encoding data on blood oxygen saturations generated byapparatus10.Signals91 may also encode information such as the charge state/remaining life of a battery power supply70, the condition ofemitter30 anddetector40, and the degree of transparency ofoptical window29 so as to assess the amount of cellular or proteneous matter coating the window.Communication device90 can also be used to reprogram controller50 and/ormemory device80.

Various embodiments of the invention also provide an external device100 for monitoring signals91. External device100 may also be configured for two-way communication withdevice10 including receivingsignals91 and sending signals92. External device100 can comprise a portable communication device101 for wireless communication withapparatus10. In various embodiments, portable device101 may correspond to a cell phone, a PDA, notepad or other like device. External device100 may also be configured to be inductively coupled to conductive coil72 so as to recharge embodiments of a rechargeable power supply70. In various embodiments external device100 may be configured to monitor and communicate withmultiple apparati10. In these and related embodiments, eachapparatus10 can be configured to have a distinct RF communication frequency and/or an identifying signal93. External device100 may be configured to simultaneously monitorapparati10, or to do so serially for example, by cycling through a range of selected frequencies corresponding to those used byindividual apparatus10.

In another aspect of the invention, embodiments of the invention provide a means for removingapparatus10 from a tissue site TS using magnetic force. Referring now toFIGS. 8a-8sc, in various embodiments,apparatus10 may include amagnetic hook75 positioned within or onhousing20 to allow the apparatus to be removed from the tissue site TS, for example by a removal tool210 (or other removal means210) including amagnet220.Magnetic hook75 can comprise magnetized material or can comprise non-magnetic ferrous material. In some embodiments,magnetic hook75 may comprise coil72 as discussed above. The force of magnetic attraction betweenmagnetic hook75 and magnetic220 is configured to be sufficient to pull theapparatus10 from the tissue site to the skin surface (i.e., beneath the skin surface) so thatapparatus10 can be readily removed from tissue site TS with a very shallow incision in the skin (or in some cases, no incision at all). Theremoval tool210 will typically include afinger grippable shaft230 or grippable means230 to whichmagnet220 is attached, allowing a physician to have finer control over movement ofsecond magnet220. In alternative embodiments,removal tool210 may comprisemagnet220 itself without a shaft.Magnet220 can also be an adjustable electromagnet allowing the physician to adjust the amount of magnetic force used to remove the apparatus. In alternative embodiments,magnetic hook75 may comprise a ferrous based suture orwire76, herein a “pull wire”76, attached to the exterior surface ofhousing20 which allows the physician to first pull the wire or suture to the skin surface usingremoval tool210 and then pull the apparatus out to the tissue surface using thepull wire76. In some embodiments, thepull wire76 can include a loop on its non-attached end to facilitate grasping of the wire once it is brought near the skin surface. The benefits of usingpull wire76 include one or more of the following: i) less magnetic force is required to remove the pull wire to skin surface then thewhole housing20 allowing use of a lesspowerful magnet220; and ii) the physician can more easily and controllably remove theentire apparatus10 using thepull wire76 then by magnetic attraction alone which should reduce both tissue trauma and pain. In some embodiments, a combination of an internalmagnetic hook75 and a ferrous-basedpull wire76 can be used to further facilitate atraumatic removal of the apparatus. Removal of the apparatus can also be facilitated by fabricating portions of thehousing20 from radio-opaque, echogenic or other materials visible under a selected medical imaging modality and/or attaching to the housing one or more medical imaging markers such as radio-opaque and/or echogenic markers.

Referring now toFIG. 9, in yet another aspect of the invention, embodiments of the invention provide akit300 for measuring blood oxygen saturation comprising embodiments of the oxygensaturation measurement apparatus10 described herein andinstructions310 for usingapparatus10.Instructions310 may include instructions and other information for using the apparatus alone and/or in conjunction with portable monitoring device101 described herein which allows a medical care giver to monitorsignals91 transmitted fromapparatus10 which include information on measured oxygen saturation or other biometric data. Theinstructions310 may either be in printed form or an electronically storedform311 stored inelectronic media312 including for example, the internet, CD-ROM, or a memory device such as a flash drive which is supplied withkit300. For embodiments using electronically stored form ofinstructions311, the instructions can be downloaded onto communication device101 using the internet or uploaded from a flash drive or CD-ROM or other electronic storage media. Theinstructions310 may include specific instruction for establishing a communications link between theapparatus10 and the portable monitoring device101 which can be a custom device or an off the shelf device such as a cell phone, notepad (e.g., an APPLE IPAD) or PDA like device. Further, specific embodiments ofinstructions300 can describe how to couple and use theapparatus10 with one or more of an APPLE IPHONE, IPAD, IPOD or like portable device running one or more software applications for deep vein thrombosis detection.

Further in various embodiments,instructions310 may include specific instructions for performing one or more of the following: i) calibrating the apparatus, ii) taking baseline oxygen saturation measurements, iii) how to use the apparatus to detect various conditions such as deep vein thrombosis; iv) how to read and/or interpret a display of the portable monitoring device to determine the presence of a deep vein thrombosis or other condition, for example instruction for reading/interpretting a graph, numerical value, symbol or message on the display.

Conclusion

The foregoing description of various embodiments of the invention has been presented for purposes of illustration and description. It is not intended to limit the invention to the precise forms disclosed. Many modifications, variations and refinements will be apparent to practitioners skilled in the art. For example, various embodiments of the apparatus can be adapted for measurement of other blood gases and any number of bio-analytes (e.g., blood sugar, glycolated hemoglobin) which may correspond to biomarkers of various conditions (e.g., hypoglycemia, hyperglycemia, etc.). Further various embodiments may also be configured for one or more ventinary applications, such as for example use in a canine, feline, equine, bovine or other farm animal. Such application can include use of one or more wireless transmission devices such an RF transmitter or wireless transmission means so that that condition of an animal or animals can be monitored remotely.

Elements, characteristics, or acts from one embodiment can be readily recombined or substituted with one or more elements, characteristics or acts from other embodiments to form numerous additional embodiments within the scope of the invention. Moreover, elements that are shown or described as being combined with other elements, can, in various embodiments, exist as standalone elements. Hence, the scope of the present invention is not limited to the specifics of the described embodiments, but is instead limited solely by the appended claims.

Claims (38)

What is claimed is:

1. An implantable apparatus for measuring blood oxygen saturation levels in a patient, the apparatus comprising:

a housing having a wall and an interior volume, at least a portion of the housing wall comprising an optically transparent material, the housing having a size, shape and column strength to be injected through and released from a hollow tissue penetrating device into an intramuscular target tissue site beneath a skin of the patient by the application of a force on a proximal end of the housing;

an optical emitter positioned within the housing, the emitter arranged and configured to emit light through the housing wall and into the tissue site to measure a blood oxygen saturation within the tissue site, the emitted light having at least one wavelength whose absorbance is related to a level of blood oxygen saturation;

an optical detector positioned within the housing and arranged to receive light reflected from the tissue site, the optical detector configured to detect light at the at least one wavelength and generate a detector output signal responsive to an intensity of the detected light;

a processor positioned within the housing and operably coupled to the detector and emitter to send signals to the emitter to emit light and receive the detector output signal, the processor including logic for calculating a blood oxygen saturation level using the detector output signal and generating a signal encoding the blood oxygen saturation level and logic to adjust at least of an intensity or wavelength of the emitted light to penetrate a selectable depth into tissue at the target site; and

a power source positioned within the housing for powering at least one of the processor, the emitter or the detector, the power source coupled to at least the processor.

2. The apparatus ofclaim 1, wherein the housing has a substantially tubular shape.

3. The apparatus ofclaim 1, wherein the tissue penetrating device comprises a syringe.

4. The apparatus ofclaim 3, wherein the syringe includes a needle and the housing is configured to be injected into the tissue site through the needle.

5. The apparatus ofclaim 1, wherein the optically transparent material comprises glass or an optically transparent polymer.

6. The apparatus ofclaim 1, wherein the optically transparent material is positioned in an optical window comprising a portion of the housing wall.

7. The apparatus ofclaim 1, wherein the housing includes a coating for reducing tissue adhesion to a housing exterior surface.

8. The apparatus ofclaim 7, wherein the coating comprises a corticosteroid or dexamethasone.

9. The apparatus ofclaim 1, wherein the power source comprises a portable battery, a lithium ion battery, a capacitor or a super capacitor.

10. The apparatus ofclaim 1, further comprising an induction device operably coupled to the power source for recharging the power source using an external electromagnetic signal.

11. The apparatus ofclaim 10, wherein the induction device comprises an induction coil.

12. The apparatus ofclaim 1, further comprising an RF communication device operably coupled to the processor, the RF communication device configured to generate and transmit an RF signal corresponding to the blood oxygen saturation signal.

13. The apparatus ofclaim 12, wherein the RF communication device sends the RF signal responsive to a signal external to the patient's body.

14. The apparatus ofclaim 12, wherein the RF communication device is configured to communicate with a portable monitoring device or cell phone.

15. The apparatus ofclaim 1, wherein the at least one wavelength comprises at least a first and a second wavelength.

16. The apparatus ofclaim 15, wherein the first wave length is in a range of about 600 to about 750 nm.

17. The apparatus ofclaim 15, wherein the second wave length is in a range of about 850 to about 1000 nm.

18. The apparatus ofclaim 1, wherein the detector comprises a photomultiplier or a charge coupled device.

19. The apparatus ofclaim 1, wherein the emitter is configured to emit light which penetrates at least about 1 cm into the tissue site.

20. The apparatus ofclaim 1, wherein the emitter is configured to emit light which penetrates at least about 2 cm into the tissue site.

21. The apparatus ofclaim 1, wherein the emitter comprises an LED.

22. The apparatus ofclaim 1, further comprising:

a modulation device operably coupled to the detector, the modulation device configured to modulate the output signal from the detector into an electrical signal having a frequency.

23. The apparatus ofclaim 22, further comprising an RF communication device operably coupled to the modulation device, the RF communication device configured to transmit an RF signal corresponding to the electrical signal.

24. The apparatus ofclaim 1, further comprising:

a magnetic hook coupled to the housing for removal of the apparatus from the tissue site by a removal tool containing a magnetized portion.

25. The apparatus ofclaim 24, wherein the magnetic hook comprises at least one of a ferrous material or a magnet.

26. The apparatus ofclaim 1, wherein the housing includes a biodegradable tissue penetrating attachment.

27. A system for detection of deep vein thrombosis of a patient, the system comprising:

the apparatus ofclaim 1; and

a monitoring device configured to receive an input from the apparatus and process the input into an output for indicating the presence of deep vein thrombosis.

28. The system ofclaim 27, wherein the monitoring device includes a display configured to display the output.

29. The system ofclaim 27, wherein the output is displayed on a graph.

30. The system ofclaim 27, wherein the apparatus wirelessly signals the input to the monitoring device.

31. A kit for detection of deep vein thrombosis of a patient, the kit comprising:

the apparatus ofclaim 1; and

instructions for using the apparatus ofclaim 1 with a portable device in order to detect deep vein thrombosis.

32. A method for measuring a blood oxygen saturation level, in a patient, the method comprising:

penetrating a hollow tissue penetrating device through a patient's skin to an intramuscular target tissue site;

injecting through the hollow tissue penetrating device to the target tissue site in the patient an apparatus for measuring blood oxygen saturation level, wherein injecting comprises applying a sufficient force on a proximal end of the housing of the apparatus to cause a distal end of the apparatus to penetrate through tissue to reach the target tissue site; and

measuring an oxygen saturation level of the target tissue site using the implanted apparatus, wherein said measuring comprises emitting light into tissue from the implanted apparatus and at least one of an intensity or wavelength of the emitted light are adjusted to penetrate a selectable depth into tissue so as to measure oxygen saturation of tissue at the selectable depth.

33. The apparatus ofclaim 1, where a column strength of the housing is in a range of about one to five pounds.

34. The method ofclaim 32, where the force applied to the proximal end of the housing is in a range of about one to five pounds.

35. An implantable apparatus for measuring blood oxygen saturation levels in a patient, the apparatus comprising:

a housing having a wall, an interior volume, an atraumatic distal end and a biodegradable tissue penetrating element attached to the atraumatic distal end of the housing so that the atraumatic distal end and the biodegradable distal end can be injected attached together into tissue, at least a portion of the housing wall comprising an optically transparent material, the housing having a size, shape and column strength to be injected through and released from a hollow tissue penetrating device into a target tissue site beneath a skin of the patient by the application of a force on a proximal end of the housing; wherein after release of the housing into tissue, the biodegradable tissue penetrating element degrades at the tissue site to reveal the atraumatic distal end of the housing;

an optical emitter positioned within the housing, the emitter arranged and configured to emit light through the housing wall and into the tissue site to measure a blood oxygen saturation within the tissue site, the emitted light having at least one wavelength whose absorbance is related to a level of blood oxygen saturation;

an optical detector positioned within the housing and arranged to receive light reflected from the tissue site, the optical detector configured to detect light at the at least one wavelength and generate a detector output signal responsive to an intensity of the detected light;

a processor positioned within the housing and operably coupled to the detector and emitter to send signals to the emitter to emit light and receive the detector output signal, the processor including logic for calculating a blood oxygen saturation level using the detector output signal and generating a signal encoding the blood oxygen saturation level; and

a power source positioned within the housing for powering at least one of the processor, the emitter or the detector, the power source coupled to at least the processor.

36. The implantable apparatus ofclaim 1, wherein the penetration depth of emitted light into tissue is up to about 3 cm.

37. The implantable apparatus ofclaim 36, wherein the penetration depth of emitted light into tissue is up to about 0.5, 1 or 2 cm.

38. An implantable apparatus for measuring blood oxygen saturation levels in a patient, the apparatus comprising:

a housing having a wall and an interior volume, at least a portion of the housing wall comprising an optically transparent material, the housing having a size, shape and column strength to be injected through and released from a hollow tissue penetrating device into an intramuscular tissue site beneath a skin of the patient by the application of a force on a proximal end of the housing;

an optical emitter positioned within the housing, the emitter arranged and configured to emit light through the housing wall and into the tissue site to measure a blood oxygen saturation within the tissue site, the emitted light having at least one wavelength whose absorbance is related to a level of blood oxygen saturation;

an optical detector positioned within the housing and arranged to receive light reflected from the tissue site, the optical detector configured to detect light at the at least one wavelength and generate a detector output signal responsive to an intensity of the detected light; wherein the optical detector and optical emitter are linearly arranged with respect to a length of the housing and recessed below the housing wall so as to produce a selected angle of light incidence and reflection with a target tissue site;

a processor positioned within the housing and operably coupled to the detector and emitter to send signals to the emitter to emit light and receive the detector output signal, the processor including logic for calculating a blood oxygen saturation level using the detector output signal and generating a signal encoding the blood oxygen saturation level; and

a power source positioned within the housing for powering at least one of the processor, the emitter or the detector, the power source coupled to at least the processor.

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